01 - Preheat oven to 300°F.
02 - Combine olive oil, melted butter, sage, garlic, lemon juice, lemon zest, salt, and pepper in a bowl to create the marinade.
03 - Pat turkey legs dry and rub marinade evenly over each leg.
04 - Spread sliced onion, carrots, and celery in a roasting pan; place turkey legs on top and pour broth around them, avoiding pouring over the legs.
05 - Cover pan tightly with foil and roast for 2 hours, basting once halfway through.
06 - Remove foil, increase oven to 400°F, and roast uncovered for 15 minutes until skin is golden and crisp.
07 - Let turkey legs rest for 5–10 minutes before serving; spoon pan juices and vegetables over each portion.